Revert task flag re-ordering, add comments

Roland points out that the flags end up having non-obvious dependencies
elsewhere, so revert aa55a08687059aa169d10a313c41f238c2070488 and add
some comments about why things are as they are.

We'll just have to fix up the broken comparisons. Roland has a patch.

Signed-off-by: Linus Torvalds <torvalds@osdl.org>

include/linux/sched.h

@@ -107,14 +107,26 @@ extern unsigned long nr_iowait(void);
 
 #include <asm/processor.h>
 
+/*
+ * Task state bitmask. NOTE! These bits are also
+ * encoded in fs/proc/array.c: get_task_state().
+ *
+ * We have two separate sets of flags: task->state
+ * is about runnability, while task->exit_state are
+ * about the task exiting. Confusing, but this way
+ * modifying one set can't modify the other one by
+ * mistake.
+ */
 #define TASK_RUNNING		0
 #define TASK_INTERRUPTIBLE	1
 #define TASK_UNINTERRUPTIBLE	2
-#define TASK_NONINTERACTIVE	4
-#define TASK_STOPPED		8
-#define TASK_TRACED		16
-#define EXIT_ZOMBIE		32
-#define EXIT_DEAD		64
+#define TASK_STOPPED		4
+#define TASK_TRACED		8
+/* in tsk->exit_state */
+#define EXIT_ZOMBIE		16
+#define EXIT_DEAD		32
+/* in tsk->state again */
+#define TASK_NONINTERACTIVE	64
 
 #define __set_task_state(tsk, state_value)		\
 	do { (tsk)->state = (state_value); } while (0)